This invention relates generally to methods and apparatus providing advanced operating features for audio and/or video programs recorded on disk media.
Various devices have been developed to enable consumers to record video and audio programs for later presentation. Such devices include tape recorders, video cassette recorders, recordable compact disks, hard drives and most recently, recordable digital video disks (DVD). A DVD that can be recorded on only once, and thereafter is essentially a DVD read only memory, is referred to by the acronym DVDxe2x88x92R. The acronym DVDxe2x88x92R is also used generally to refer to the write-once, or record-once, technology. Several formats are available for DVD""s to be recorded on, erased and re-recorded, that is overwritten or rewritten. These are referred to by the acronyms DVDxe2x88x92RAM, DVDxe2x88x92RW and DVD+RW. As of this time no uniform industry standard has been adopted. The acronyms DVDxe2x88x92RAM, DVDxe2x88x92RW and DVD+RW are also used generally to refer to the respective rewritable technology. Reference herein to rewritable DVD technology, devices and methods is generally intended to encompass all of the standards which are now being used, as well as those which may be developed in the future.
In many cases, the program presentations are recorded in the viewer and/or listener""s absence, for presentation at a later, more convenient time. This is referred to as time shifting the program. At other times, a program is being viewed and/or listened to without being recorded, and with out any interest in a recording, but the viewer""s and/or listener""s attention is interrupted, for example by a telephone call or an unexpected visitor. If the viewer and/or listener is watching a television program, for example, and has a cassette tape in a VCR, or can retrieve and load such a cassette tape quickly, the program can be recorded. However, the viewer and/or listener cannot view and/or listen to the program in its entirety, and in a proper time sequence, until after the recording has been completed. The time to completion of the recording can be short or long, depending on the length of the program.
A desirable feature in a DVD device would enable a viewer and/or listener to initiate resumption of the program presentation as soon as the interruption or pause has ended, without sacrificing the program content during the interruption or pause.
Although rewritable DVD technology is generally available, operation is limited to such basic functions as play, record, fast forward reverse and stop. Pause is available, but only as a counterpart to pause operation in a VCR, for example interrupting the play back of a prerecorded program or interrupting the recording of a viewed program to eliminate commercials from the recording. Unlike computer hard drives, recordable DVD devices have a very significant additional function, which is playing back prerecorded DVD""s. Thus, there is an economic incentive to develop rewritable DVD technology, including methods and devices, that can be used instead of a computer hard drive. It is a challenge to provide such devices with improved, advantageous features without compromising the goal of decreasing costs and increasing sales. Such novel DVD features should include the ability to simultaneously view and record on a disk medium in a seamless fashion, without the high operating speed of a computer hard drive. A recordable DVD device with a single head for reading and writing cannot read and write simultaneously. Accordingly, the terms seamless and simultaneous are used herein to denote that recording and playing back program material in accordance with the inventive arrangements has the appearance of being simultaneous to the viewer and/or listener, even though the functionality is actually alternating or multiplexed.
Another issue relates to the number of times program material can be recorded and re-recorded on disk media, particularly the same DVD. Persistent recording in the same section of the disk will exhaust the lifetime of the disk prematurely. It is desirable when implementing novel features, particularly features that can require large amounts of overwriting, to prevent persistent recording in the same sections of a rewritable DVD to prevent premature exhaustion.
Another issue relates to the maximum data rates of minimally capable rewritable DVD devices. A basic rewritable DVD device, having for example a 1xc3x97(one times) read and a 1xc3x97(one times) write capability, typically has maximum data rates for recording or playing back of approximately 11 megabits/second. Accordingly, it is desirable to implement novel features that can be implemented within the constraints of the maximum available data rates.
A method in accordance with the inventive arrangements for managing buffers in an apparatus adapted for writing program portions onto and reading said program portions from a digital program disk, comprises the steps of: filling a first buffer with encoded program portions at a first bit rate; filling a second buffer with said encoded program portions read from said digital program disk; supplying said encoded program portions from said second buffer for decoding; and, establishing an initial complementary fullness of said first and second buffers using an excess bit rate capability of said apparatus related to said first bit rate.
Another method in accordance with the inventive arrangements for initiating apparently simultaneous recording on and playing back from a digital program disk, comprises the steps of: buffering program portions before writing the program portions onto the digital program disk; buffering the program portions after reading from the digital program disk; upon receiving a command, jumping a read/write pickup assembly between first and second locations spaced from one another along a track of the digital program disk; during the jumping, accumulating the program portions not yet written onto the digital program disk during the first-mentioned buffering step; after the jumping, initiating reading and accumulating at least one of the program portions read from the digital program disk during the second-mentioned buffering step; and, accumulating a predetermined sum of the program portions during both the buffering steps.
The predetermined sum of program portions is maintained during the buffering steps by complementary operation. When program portions are accumulated during the first-mentioned buffering step, program portions are depleted during the second-mentioned buffering step. Similarly, when program portions are accumulated during the second-mentioned buffering step, program portions are depleted during the first-mentioned buffering step.
An apparatus in accordance with the inventive arrangements for alternately writing onto and reading program portions from a digital program disk during apparently simultaneous recording and playing back, comprises: a first signal processing path for receiving and encoding the program; a read/write pickup assembly for writing encoded program data onto the digital program disk and reading encoded program data from the digital program disk; a servo system for the pickup assembly; a second signal processing path for decoding and playing back the encoded program; a first buffer for storing encoded program portions ready to be written onto the digital program disk; a second buffer for storing encoded program portions read from the digital program disk; and, a controller having a first mode of operation for recording the program portions onto alternate segments of the track, during which the first buffer is free running, a second mode of operation for initiating complementary operation of the first and second buffers during and after a jump by the pickup assembly and a third mode of operation for maintaining the complementary operation.
A predetermined sum of program portions stored in the buffers is established during the second mode of operation and maintained during the third mode of operation. When program portions are accumulated in the first buffer, program portions are depleted from the second buffer. Similarly, when program portions are accumulated in the second buffer, program portions are depleted from the first buffer.
In accordance with the inventive arrangements, a read/write pickup assembly for a digital program disk, for example a rewritable DVD device, can make long jumps between locations spaced from one another along a track of a digital program disk. This is useful, for example, during the course of simultaneously recording and playing back the same program or playing back a first program and recording another program. Such a feature advantageously enables the switching between writing onto the DVD and reading from the DVD to be multiplexed in such a way as to be transparent to the viewer and/or listener. Even though a single pickup assembly cannot write and read simultaneously, the recording and playing back can be made to appear simultaneous by advantageous management of buffers in the input and output signal processing paths. Simultaneous recording and playing back is a very desirable feature that enables several advantageous modes of operation. One such mode is a record during pause and play, which can also be referred to as a pause during record and play. Another such mode is recording a first program while viewing a second program, utilizing the same DVD.
The inventive arrangements are also applicable to related kinds of disk media, for example rewritable CD-ROM and computer-type hard drives.